Method and apparatus for controlling call volume

ABSTRACT

A method and apparatus for controlling a call volume for an office that serves as a protecting site for another office in a packet network are disclosed. For example, the method collects one or more customer registration counts from one or more session border controllers located in a first office, determines if the one or more customer registration counts have reached or exceeded a threshold. The method directs all of said one or more session border controllers located in said first office to enact one or more throttling rules if the one or more customer registration counts have reached or exceeded the threshold.

This application is a continuation of U.S. patent application Ser. No.14/709,042 , filed May 11, 2015, now U.S. Pat. No. 9,954,780, which is acontinuation of U.S. patent application Ser. No. 12/189,648, filed Aug.11, 2008, now U.S. Pat. No. 9,031,217, which are herein incorporated byreference in their entirety.

The present invention relates generally to communication networks and,more particularly, to a method for controlling call volume for anoffice, e.g., for an access office, that serves as a protecting site foranother office in a packet network, e.g., an Internet Protocol (IP)network or Voice over Internet Protocol (VoIP) network.

BACKGROUND OF THE INVENTION

A large scale service provider network, e.g., a Next Generation Network(NGN), may comprise multiple regional access offices connected to abackbone network, e.g., an Internet Protocol (IP) backbone network. Theservice provider may enable an access office to serve as a protectionsite for another access office. For example, if a network failureaffects the ability to reach a first access office, the service providermay enable a second access office to serve as a protection site suchthat customers who typically register at the first access office mayutilize the second access office in the event of a failure. However, themajority of calls (outbound and inbound) for the customers whore-register at a protection site are for a customer phone number servedby the first access office. For example, the majority of calls betweenre-registered (re-homed) customers and Public Switched Telephone Network(PSTN) phone numbers are served by media gateways in the first accessoffice. Hence, the majority of voice media packets for calls for there-homed customers associated with PSTN phone numbers will traverselinks between one or more access offices and the backbone networkmultiple times. In other words, the re-homed customers will use thesecond access office to reach the first access office. This increase intraversals due to the re-homing of a portion of the customers for theservice provider consumes a significant capacity of the network.

In some failure scenarios, e.g., failure of all public connections to afirst access office, a large number of customers may be affected. If alarge number of customers re-register at one or more session bordercontrollers located at the protection site for the access office, themajority of calls for the re-homed customers for PSTN phone numbers maystill need to use media gateways in the first access office. Thus, amassive number of customers re-registering at the protection site mayresult in the network being overloaded and performance being degradedfor all calls.

SUMMARY OF THE INVENTION

In one embodiment, the present invention discloses a method andapparatus for controlling a call volume for an office that serves as aprotecting site for another office in a packet network. For example, themethod collects one or more customer registration counts from one ormore session border controllers located in a first office, determines ifthe one or more customer registration counts have reached or exceeded athreshold. The method directs all of said one or more session bordercontrollers located in said first office to enact one or more throttlingrules if the one or more customer registration counts have reached orexceeded the threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

The teaching of the present invention can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates an exemplary network related to the presentinvention;

FIG. 2 illustrates an exemplary network with one embodiment of thepresent invention for controlling call volume for an office;

FIG. 3 illustrates a flowchart of a method for controlling call volumefor an office that serves as a protecting site for another office;

FIG. 4 illustrates a flowchart of a method for throttling calls; and

FIG. 5 illustrates a high-level block diagram of a general-purposecomputer suitable for use in performing the functions described herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

The present invention broadly discloses a method and apparatus forcontrolling call volume for an office, e.g., an access office, thatserves as a protecting site for another office. Although the presentinvention is discussed below in the context of an IP MultimediaSubsystem (IMS) network, the present invention is not so limited.Namely, the present invention can be applied to all networks capable ofsupporting Voice over Internet Protocol (VoIP) and the like.

FIG. 1 illustrates an exemplary network 100 related to the currentinvention. The exemplary network 100 may be used to support callsbetween Internet Protocol (IP) based and Time Division Multiplexing(TDM) based customer endpoint devices. For example, the illustrativenetwork 100 may comprise IP based User Endpoint (UEs) 121-123 connectedto a carrier (e.g., a service provider) Next Generation Network (NGN) toaccess services, e.g., VoIP services and the like. For example, thenetwork 100 may be used to support a call between an IP based UE 121,122 or 123 and a TDM based Public Switched Telephone Network (PSTN)endpoint 124.

In one embodiment, the NGN includes regional access offices 114 and 115connected to the IP backbone network 110. The IP backbone network 110may comprise a public network 111 and an internal network 112. Networkaddresses (e.g. router addresses) within the internal network 112 arereachable using routing information available only within the serviceprovider's network. The public network 111 comprises the network portionreachable using routing information (e.g. IP addresses) available inpublic domain.

The IP backbone network 110 also comprises Provider Edge (PE) routers116 and 117. The PE routers 116 and 117 may provide routing for both thepublic and internal networks 111 and 112. Specifically, PE router 116 islogically segmented into a portion for supporting public connections 131and a portion for supporting internal connections 133. Similarly, PErouter 117 is logically segmented into a portion supporting for publicconnections 132 and a portion for supporting internal connections 134.To simplify the present disclosure, the portion for supporting publicconnections and the portion for supporting internal connections will bereferred to as simply public connections and internal connections.

In one embodiment, regional access offices 114 and 115 are used forhosting one or more network devices such as Session Border Controllers(S/BC), Media Gateways (MGWs), Customer Edge (CE) routers, and the likein a distributed manner. Note that an access office may host any numberof media gateways, any number of S/BCs, etc. In addition, the number andtype of devices hosted at each access office may be different.

In one embodiment, the Session Border Controllers (S/BCs) are used toenable IP UEs to connect to the NGN 109 for obtaining services. Forexample, a UE may register at a particular S/BC to receive VoIPservices. Each S/BC bridges between the public network 111 and theinternal network 112. Once a UE registers at a particular S/BC, callsto/from the UE flow through that particular S/BC at which the UE isregistered. The particular S/BC will then perform the bridging of thecall between the public and internal networks for the registered UE.

In one embodiment, the MGWs are used to support calls between the IPbased UEs and TDM based PSTN endpoints. For example, calls to or from aPTSN phone use a particular trunk group on a particular MGW, dependingon the PSTN number. The PSTN number refers to a phone number. Forexample, in phone numbers derived from the North American Numbering Plan(NANP), the phone number is a 10 digit number. The area code is thefirst three digits, and is also referred to as a Numbering Plan Area(NPA) code. The term NPA.NXX refers to the first six digits of a phonenumber containing the NPA code and a three digit exchange numberfollowing the area code. Calls to and from a particular NPA.NXX may thenuse a particular trunk group on a particular MGW. For example, MGW 146may handle calls to/from the PSTN phone 124.

In network 100, regional access office 114 hosts CE router 141, sessionborder controllers 143 a and 143 b and media gateway 145. Similarly,regional access office 115 hosts CE router 142, session bordercontroller 144 and media gateway 146. Each regional access office 114 or115 is connected to the IP backbone network 110 via a PE router, e.g.,PE 116 or 117, over both public and internal connections. Namely, CErouter 141 is connected to the public connections 131 on PE router 116over a public link, e.g., over the Internet. CE router 141 is alsoconnected to the internal connections 133 on PE router 116 over aninternal link, e.g., an internal local area network. Similarly, CErouter 142 is connected to the public connections 132 and internalconnections 134 on PE router 117.

Packets from IP UEs 121-123 reach an access office 114 or 115 via thepublic network 111 and a public connection on either PE 116 or 117. Forexample, UE 121 may register at S/BC 143 b in access office 114. Packetsfrom UE 121 may then reach the S/BC 143 b in access office 114 via thepublic network 111, the public connections 131 located in PE 116 and CE141. Similarly, UE 123 may register at S/BC 144 in access office 115.Packets from UE 123 may then reach the S/BC 144 in access office 115 viathe public network 111, the public connections 132 located in PE 117 andCE 142.

If a call is between an IP based UE and a TDM based PSTN phone, the callis handled by the S/BC at which the UE is registered and the MGWhandling calls to/from the PSTN phone number for the specific area code,i.e. NPA code. If the S/BC and the MGW for a call are collocated in thesame access office, the call traverses the link between the PE routerand the CE router once. If the S/BC and the MGW for a call are locatedin different access offices, the call traverses the link between the PErouter and CE router in the access office with the S/BC twice and thelink between the PE router and CE router in the access office with theMGW once.

In one example, a call is originated by UE 121 registered at S/BC 143 b.The call is destined to a PSTN phone 124 and MGW 145 handles the areacode (NPA) for the PSTN endpoint 124. A call path 151 illustrates thepath traversed by packets between UE 121 and PSTN endpoint 124. Forexample, the call originated by UE 121 traverses PE 116 and CE 141 toreach S/BC 143 b. S/BC 143 b bridges the call to the internal networkand forwards the call to MGW 145 via CE 141. The MGW 145 may thenforward the call to the PSTN endpoint 124 via the PSTN 113.

In one example, a call is originated by UE 121 registered at S/BC 143 b.The call is destined to a PSTN endpoint 125 and MGW 146 handles the areacode (NPA) for the PSTN endpoint 125. A call path 152 illustrates thepath traversed by packets to/from UE 121 from/to PSTN phone 125. Thecall originated by UE 121 traverses PE 116 and CE 141 to reach S/BC 143b. S/BC 143 b bridges the call to the internal network and forwards thecall to MGW 146 via CE 141, PE 116 (internal connections 133), internalnetwork 112, PE 117 (internal connections 134) and CE 142. The MGW 146may then forward the call to the PSTN endpoint 125 via the PSTN 113.

As illustrated in the above example, when the S/BC and MGW for a callare in different access offices, twice as much bandwidth is required inthe access office with the S/BC, as compared to the bandwidth requiredfor an access office where both the S/BC and MGW are collocated. Generalphone call statistics shows that the majority of phone calls are localcalls. Accordingly, network service providers may design their accessoffices placing S/BCs and MGWs such that the majority of calls betweenIP based UEs and TDM based PSTN endpoints traverse collocated S/BCs andMGWs. However, the network may be designed to handle a specific fractionof calls traversing an S/BC and an MGW in different access offices. Forexample, the network may be engineered to handle approximately 10% ofcalls traversing an S/BC and an MGW in different access offices.

If a UE is unable to register or it loses connectivity to the S/BC thatnormally services it, the UE may register at another S/BC and continueaccessing services. The re-registering at another S/BC may also bereferred to as re-homing. Note that the MGW is connected via theinternal network. The re-homed UEs may continue originating andreceiving calls to/from the PSTN phone numbers using the MGW in oneaccess office, but another S/BC in a different access office. Forexample, if the UE was typically calling PSTN phone numbers with areacode 212 and the MGW handling the area code 212 was located in a firstaccess office as the S/BC at which the UE was originally registered,after re-homing by registering at another S/BC located at a secondaccess office, the UE's calls to area code 212 will be handled by theS/BC located at the second office and the MGW in the first office. Thatis, the majority of calls to/from re-homed UEs will flow via an S/BC andan MGW in different access offices.

In one embodiment, a service provider may enable an access office toserve as a protection site for another access office. For example, if anetwork failure affects access to a first access office, the serviceprovider may enable a second access office to serve as a protection sitesuch that customers who typically use the first access office mayutilize the second access office. However, in some failure scenarios,the public network connection to an access office may be affected by afailure while the internal portion is functioning normally. A largenumber of UEs may then re-home to a protection site (another accessoffice) resulting in a massive re-homing event. A massive re-homingevent refers to a network event in which a pre-determined large numberor percentage of UEs registered at one or more S/BCs in a first accessoffice re-register at one or more S/BCs located at another access office(e.g., a second access office) serving as a protection site for thefirst access office.

As discussed above, the majority of PSTN calls to/from the re-homed UEsis for an area code that is serviced by a MGW in the first accessoffice. Since these calls require more network bandwidth as explainedabove, a massive re-homing event may result in the network beingoverloaded, performance being degraded, etc. for all calls. For example,calls that are normally handled by the protection site may experienceincreased delay, packet loss, and the like, due to the increased numberof calls resulting from the massive re-homing event.

In one embodiment, the current invention provides a method forcontrolling call volume for an access office that serves as a protectionsite for another access office. The method first provides a site monitorat each access office. The site monitor stores a list of NPA codes thatare handled by MGWs within the same access office. The site monitor alsonotifies all S/BCs in the same access office of the list of NPA codesthat are handled by MGWs within the same access office. If there is achange to the list, the site monitor provides updates to the S/BCsaccordingly.

In one embodiment, the site monitor also comprises a rule-engine forthrottling calls. Throttling refers to controlling the number of callsallowed between UEs and the PSTN network, other than calls to/from PSTNsphones with an NPA code served by an MGW located in the same accessoffice as the S/BC at which the UE is registered. For example, if amassive fail-over for a first access office occurs, the rule-engine in asecond access office may decide to throttle calls between re-homed UEsand PSTN networks such that the number of calls that have to use MGWs inthe first access office is controlled. This approach will minimize theimpact to UEs that are re-homed with the second access network.

In one embodiment, the service provider may populate one or morethrottling parameters in a site monitor. For example, the serviceprovider may determine the number of calls (e.g., re-homed calls orinter-access office calls) that may be allowed at any given time, thenumber of calls that may be allowed in a sliding window of time, and soon. If the service provider creates or modifies a rule for throttlingcalls and/or throttling parameters, the site monitor may provide updatesto the S/BCs located in the same access office.

In one embodiment, the service provider determines the rules forthrottling and/or populates the one or more throttling parameters basedon the number of inter-access office calls the network can support. Forexample, if it is expected that 95% of the total number of calls beinglocal calls, the network may be designed with sufficient bandwidth tohandle 100% of the total number of calls being local and with sufficientbandwidth to handle 15% of the total number of calls being to or fromother access offices. The throttling rules may be set to limit interaccess office calls to 15% for an access office. Furthermore, anotherrule may then limit calls to/from re-homed UEs to PSTNs served in otherlocations to 10%. It should be noted that these threshold values areonly illustrative and the present invention is not limited to aparticular threshold value.

In one embodiment, the site monitor will collect customer registrationcounts from S/BCs located in the same access office, e.g., periodicallyin accordance with a schedule. For example, the site monitor may collectcustomer registration counts in a pre-determined interval, e.g., every 5minutes, 15 minutes, and so on.

In one embodiment, the site monitor then aggregates the customerregistration counts over time and tracks historical data for one or morepre-determined time windows. For example, the registration counts may beaggregated over a hourly sliding time window of time to track changes.

The site monitor may then detect when a massive fail-over for an accessoffice occurs. For example, if a large number of UEs registered at afirst access office re-register at the protection site for the firstaccess office, then the method may identify or correlate the changes asa significant network event, e.g., a massive fail-over event. The sitemonitor in the protection access office will detect the sudden increaseof registered user numbers and will determine that a massive failoverhas occurred.

If a site monitor detects a massive fail-over, e.g., when apredetermined threshold is reached or exceeded, the site monitor directsall S/BCs located in the same access office to enact throttling for PSTNcalls other than those NPA codes currently being serviced by the MGWlocated in the same access office.

When throttling is enacted, an S/BC first determines if a call isbetween an internet protocol UE and a PSTN endpoint. For example, theS/BC may use the Session Description Protocol (SDP) data in the SessionInitiation Protocol (SIP) of the signaling message. If the call isbetween a UE and PSTN endpoint, the S/BC further checks to determine ifthe NPA code is supported by a MGW located in the same access office. Ifthe call is not supported by a MGW located in the same access office,the S/BC then compares the throttling rules against the historicaltracking data of similar calls. The S/BC may then either reject the callor allow the call to be setup. For example, if the tracking dataindicates that the limits for simultaneous calls in accordance with thethrottling rules have already been reached, then the call may berejected. The S/BC may then update its local tracking counters for PSTNcalls to/from other access offices.

FIG. 2 illustrates an exemplary network 200 with one embodiment of thepresent invention for controlling a call volume for an access officethat serves as a protection site for another access office. In oneembodiment, the service provider implements site monitors 247 and 248 inaccess offices 114 and 115, respectively. The service provider alsoenables the access office 114 to serve as a protection site for accessoffice 115.

The site monitor 114 stores a list of NPA codes that are handled by MGW145. The site monitor 247 also notifies S/BCs 143 a and 143 b of thelist of NPA codes that are handled by MGW 145. If there is a change tothe list of NPA codes, the site monitor 247 will provide updates to theS/BCs 143 a and 143 b accordingly.

In one embodiment, the site monitor 247 may comprise a rule-engine forthrottling calls between re-homed UEs and PSTN networks such that thenumber of calls that have to use MGWs in another access office iscontrolled. For example, the site monitor 247 collects customerregistration counts from S/BCs 143 a and 143 b periodically. The sitemonitor then aggregates the customer registration counts over time andtracks historical data for one or more pre-determined time windows. Forexample, the registration counts may be aggregated over a hourly slidingtime window, and so on.

The site monitor 247 may then detect if a massive fail-over for accessoffice 115 has occurred. For example, if a large number of UEsregistered at access office 115 re-register at access office 114, thesite monitor 247 will detect the massive fail-over events, e.g.,detecting a significant increase in the numbers of re-homed calls. Ifthe site monitor 247 detects a massive fail-over, then the site monitorwill direct S/BCs 143 a and 143 b to enact throttling for PSTN callsother than to and from those NPA codes currently serviced by the MGW145.

In one embodiment, the site monitor 247 may continue tracking the databeing received from the S/BCs to determine if the number of re-homed UEsis back to normal historical levels. For example, the access office thathad experienced the access failure may recover. In another embodiment,network operations personnel may issue a command manually to the sitemonitor 247 to disable the throttling of calls. If the condition forthrottling calls is no longer applicable, the site monitor 247 may thendisable the function of throttling calls.

When throttling is enacted, the S/BC 143 a or 143 b first determines ifa call is between an internet protocol UE and a PSTN endpoint. Forexample, the S/BC 143 b may determine that a call is between a UE and aPSTN endpoint. The S/BC 143 b will also check to determine if the NPAcode for the call is currently supported by a MGW 145. If the call isnot supported by the MGW 145, the S/BC 143 b then compares thethrottling rules against the historical tracking data of similar calls.The S/BC 143 b may then either reject the call or allow the call to besetup. For example, if the call is from UE 123 re-homed to S/BC 143 bbut the MGW being used is MGW 146 located in access office 115, then thetracking data is compared to the throttling rules. If the tracking dataindicates that the limits for simultaneous calls in accordance with thethrottling rules have already been reached for such calls, then the callwill be rejected. The S/BC 143 b may then update its local trackingcounters for PSTN calls to/from other access offices.

FIG. 3 illustrates a flowchart of a method 300 for controlling callvolume for an access office that serves as a protecting site for anotheraccess office. For example, one or more steps of method 300 can beimplemented by a site monitor. Method 300 starts in step 305 andproceeds to step 310.

In step 310, method 300 stores a list of Numbering Plan Area (NPA) codesthat are handled by one or more Media Gateways (MGWs) within the sameaccess office. For example, the method may store a list of NPA codesthat are using an MGW trunk within the same access office to reach aPublic Switched Telephone Network (PSTN) phone number.

In step 320, method 300 populates a rule engine with one or more rulesfor throttling calls. For example, a rule-engine may have a rule forthrottling calls that specifies that an S/BC throttles calls betweenre-homed UEs and PSTN networks such that the number of calls that haveto use MGWs in the first access office experiencing an access failure iscontrolled to a specific predetermined number. For example, the rule mayspecify the number (e.g., a threshold value) of PSTN calls from re-homedUEs via MGWs in the first access office where call throttling willstart, e.g., not to exceed a 1000 calls per hour, 1000 calls in anysliding time window of 1 hour, and so on.

In step 330, method 300 provides one or more Session Border Controllers(S/BCs) in the same access office: the list of NPA codes that arecurrently handled by one or more media gateways in the same accessoffice and one or more rules for throttling calls.

In step 340, method 300 collects customer registration counts from theone or more S/BCs located in the same access office in a predeterminedinterval. For example, the site monitor may collect customerregistration counts from counters in S/BCs every 5 minutes, 15 minutes,and so on.

In optional step 350, method 300 tracks customer registration countsover time. For example, the method may aggregate the customerregistration counts over various time intervals and track historicaldata for pre-determined time windows. For example, the registrationcounts may be aggregated over a hourly sliding time window to trackchanges.

In step 360, method 300 determines whether a massive fail-over for anaccess office occurred from the customer registration counts, e.g.,monitoring whether a threshold value has been reached or exceeded. Forexample, if a large number of customer UEs registered at a first accessoffice re-register at the protection site for the first access office,then the method may identify or correlate the network event as a massivefail-over event for the first access office. In another example, if thenumber of customer registration counts changes by a predeterminedpercentage, e.g., 200%, the method may determine that a massivefail-over for an access office has occurred and so on. If the methoddetermines that a massive fail-over for an access office has occurred,the method proceeds to step 365. Otherwise, the method proceeds to step380.

In step 365, method 300 determines whether throttling has previouslybeen enacted. If the query is positively answered, method 300 proceedsto step 375. Otherwise, method proceeds to step 370.

In step 370, method 300 directs all S/BCs located in the same accessoffice to enact throttling. For example, the method may direct all S/BCsin the same access office such that the number of PSTN calls other thanto and from those NPA codes currently being serviced by the MGW locatedin the same access office is controlled in accordance with thethrottling rules.

In step 375, method 300 determines if recovery is completed. Forexample, the method may determine customer registration counts are backto normal historical levels. If recovery is completed, the methodproceeds to step 377. Otherwise, the method proceeds to step 380.

In step 377, method 300 directs all S/BCs located in the same accessoffice to disable throttling. For example, the method may disablethrottling calls for an access office that has recovered. The method maythen proceed to step 380.

In step 380, method 300 determines if there is a change to one or moreof: the list of NPA codes that are handled by MGWs within the sameaccess office and rules for throttling calls. If there is no change, themethod proceeds to step 340. Otherwise, the method proceeds to step 310.

FIG. 4 illustrates a flowchart of a method 400 for throttling calls. Forexample, one or more steps of method 400 can be implemented by a sessionborder controller located in an access office that serves as aprotecting site for another access office. Method 400 starts in step 405and proceeds to step 410.

In step 410, method 400 receives a list of NPA codes that are handled byone or more media gateways in the same access office and one or morerules for throttling calls. For example, an S/BC receives a list of NPAcodes that are handled by MGWs in the same access office as the S/BC andalso receives rules for throttling calls.

In step 420, method 400 provides customer registration counts to a sitemonitor. For example, the S/BC may have counters indicating the numberof registrations by customers for predetermined intervals of time. Inone embodiment, the customer registration counts may be provided to thesite monitor in a predetermined schedule. In another embodiment, thesite monitor may send requests for customer registration counts to thesession border controllers based on its own schedule.

In step 430, method 400 receives a call. For example, the method mayreceive a Session Initiation Protocol (SIP) signaling message from acustomer with a UE initiating a call towards a user of a PSTN endpoint.

In step 440, method 400 determines if throttling is enacted. Forexample, the S/BC may have been directed by a site monitor to enactthrottling for re-homed customer PSTN calls handled by MGWs in otheraccess offices. If throttling is enacted, the method proceeds to step450. Otherwise, the method proceeds to step 490.

In step 450, method 400 determines if the received call is between a UEand a PSTN endpoint. For example, the method may process the SessionDescription Protocol (SDP) data in the received SIP signaling message todetermine if the call is between a UE and a PSTN endpoint. If the callis between a UE and a PSTN endpoint, the method proceeds to step 460.Otherwise, the method proceeds to step 490.

In step 460, method 400 determines if the NPA code for the PSTN endpointassociated with the call is supported by a MGW located in the sameaccess office. If the call is supported by a MGW located in the sameaccess office, the method proceeds to step 490. Otherwise, the methodproceeds to step 470.

In step 470, method 400 compares the one or more rules for throttlingcalls against a historical tracking data of similar calls. For example,the tracking data may indicate the limits for throttling calls have notbeen reached. For example, the throttling rule may allow 500 calls to beaccepted every hour and the tracking data may show a current call countof only 20.

In step 480, method 400 determines if the call is to be rejected. Forexample, if the limits in accordance with the rules for throttling callsare reached, the call will be rejected. If the call is allowed to besetup, then the method proceeds to step 490. Otherwise, the methodproceeds to step 485.

In step 485, method 400 rejects the call. For example, the methodprevents the call from being setup. For example, the method may reply tothe SIP signaling message with a SIP 503 message (service unavailable).The method may then proceed to step 495.

In step 490, method 400 continues processing the call. For example, themethod may proceed with setting up of the call. For example, the usersof the UE and PSTN endpoint may be able to converse once the call isallowed to be setup. The method then proceeds to step 495.

In step 495, method 400 updates local tracking counters for PSTN callsto/from other access offices. For example, if the call is accepted, themethod may update counters by incrementing the number of calls. Themethod may then proceed to step 499 to end processing the current call.Alternatively, the method may then return to step 430. It should benoted that one or more steps of method 400 may be implemented inparallel and not in sequential order as shown. For example, steps 410and 420 can be implemented in parallel and these steps can beimplemented using independent processes or threads in most modernoperating systems. As such, steps 410 and 420 will be executed indifferent time frame as well, e.g., in accordance to a predefinedschedule or in response to a request at any given time.

In one embodiment, the above method 300 may store a list of NPA-NXXcodes handled by media gateways in the same access office. The methodmay then enact throttling based on NPA-NXX codes instead of NPA codes.For example, the site monitor may enact throttling for NPA-NXX codes andnotify S/BCs in the same office.

Those skilled in the art would realize that the media gateways, S/BCs,site monitors may be located in other types of offices. For example, theterm “office” or “access office” refers to a logical grouping ofequipment as discussed above.

For example, a regional office may house these network elements forvarious NPA codes or NPA-NXX codes. In addition, a PE and CE may belocated within the same physical building. As such, the pairing of a CEand a PE and defines the relationship between the backbone and accessportions of the NGN. Therefore, the above description is not intended tolimit the implementation to a specific type of office or physicalstructure.

It should be noted that although not specifically specified, one or moresteps of methods 300 and 400 may include a storing, displaying and/oroutputting step as required for a particular application. In otherwords, any data, records, fields, and/or intermediate results discussedin the method can be stored, displayed and/or outputted to anotherdevice as required for a particular application. Furthermore, steps orblocks in FIG. 3 and FIG. 4 that recite a determining operation orinvolve a decision, do not necessarily require that both branches of thedetermining operation be practiced. In other words, one of the branchesof the determining operation can be deemed as an optional step.

FIG. 5 depicts a high-level block diagram of a general-purpose computersuitable for use in performing the functions described herein. Asdepicted in FIG. 5, the system 500 comprises a processor element 502(e.g., a CPU), a memory 504, e.g., random access memory (RAM) and/orread only memory (ROM), a module 505 for controlling call volume for anaccess office that serves as a protecting site for another accessoffice, and various input/output devices 506 (e.g., storage devices,including but not limited to, a tape drive, a floppy drive, a hard diskdrive or a compact disk drive, a receiver, a transmitter, a speaker, adisplay, a speech synthesizer, an output port, and a user input device(such as a keyboard, a keypad, a mouse, alarm interfaces, power relaysand the like)).

It should be noted that the present invention can be implemented insoftware and/or in a combination of software and hardware, e.g., usingapplication specific integrated circuits (ASIC), a general-purposecomputer or any other hardware equivalents. In one embodiment, thepresent module or process 505 for controlling call volume for an accessoffice that serves as a protecting site for another access office can beloaded into memory 504 and executed by processor 502 to implement thefunctions as discussed above. As such, the present method 505 forcontrolling call volume for an access office that serves as a protectingsite for another access office (including associated data structures) ofthe present invention can be stored on a computer readable medium, e.g.,RAM memory, magnetic or optical drive or diskette and the like.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A method for controlling a call volume in anetwork, the method comprising: determining, by a processor, a number ofcalls traversing a first access office and that utilize a media gatewayin a second access office of the network have exceeded a threshold; anddirecting, by the processor, at least one session border controllerlocated in the first access office to enact a throttling, wherein thethrottling comprises refusing to setup an inter office call, wherein theinter office call comprises a call traversing different access offices,wherein the different access offices comprise the first access officeand at least the second access office.
 2. The method of claim 1, whereinthe throttling implements a throttling rule that is based on a number ofinter office calls that the network is able to support.
 3. The method ofclaim 1, wherein the throttling is based on a number of inter officecalls that are allowed at any given time.
 4. The method of claim 1,wherein the inter office call is determined from a numbering plan areacode.
 5. The method of claim 1, wherein the network is a packet network.6. The method of claim 1, further comprising: disabling the throttlingwhen the number of calls traversing the first access office and thatutilize the media gateway in the second access office of the networkhave fallen below the threshold.
 7. The method of claim 1, wherein anumber of inter office calls is determined from a numbering plan areacode plus an exchange number.
 8. A tangible computer-readable medium forstoring instructions which, when executed by a processor, cause theprocessor to perform operations for controlling a call volume in anetwork, the operations comprising: determining a number of callstraversing a first access office and that utilize a media gateway in asecond access office of the network have exceeded a threshold; anddirecting at least one session border controller located in the firstaccess office to enact a throttling, wherein the throttling comprisesrefusing to setup an inter office call, wherein the inter office callcomprises a call traversing different access offices, wherein thedifferent access offices comprise the first access office and at leastthe second access office.
 9. The tangible computer-readable medium ofclaim 8, wherein the throttling implements a throttling rule that isbased on a number of inter office calls that the network is able tosupport.
 10. The tangible computer-readable medium of claim 8, whereinthe throttling is based on a number of inter office calls that areallowed at any given time.
 11. The tangible computer-readable medium ofclaim 8, wherein the inter office call is determined from a numberingplan area code.
 12. The tangible computer-readable medium of claim 8,wherein the network is a packet network.
 13. The tangiblecomputer-readable medium of claim 8, the operations further comprising:disabling the throttling when the number of calls traversing the firstaccess office and that utilize the media gateway in the second accessoffice of the network have fallen below the threshold.
 14. The tangiblecomputer-readable medium of claim 8, wherein a number of inter officecalls is determined from a numbering plan area code plus an exchangenumber.
 15. An apparatus for controlling a call volume in a network, theapparatus comprising: a processor; and a tangible computer-readablemedium in communication with the processor storing instructions which,when executed by the processor, cause the processor to performoperations, the operations comprising: determining a number of callstraversing a first access office and that utilize a media gateway in asecond access office of the network have exceeded a threshold; anddirecting at least one session border controller located in the firstaccess office to enact a throttling, wherein the throttling comprisesrefusing to setup an inter office call, wherein the inter office callcomprises a call traversing different access offices, wherein thedifferent access offices comprise the first access office and at leastthe second access office.
 16. The apparatus of claim 15, wherein thethrottling implements a throttling rule that is based on a number ofinter office calls that the network is able to support.
 17. Theapparatus of claim 15, wherein the throttling is based on a number ofinter office calls that are allowed at any given time.
 18. The apparatusof claim 15, wherein the inter office call is determined from anumbering plan area code.
 19. The apparatus of claim 15, the operationsfurther comprising: disabling the throttling when the number of callstraversing the first access office and that utilize the media gateway inthe second access office of the network have fallen below the threshold.20. The apparatus of claim 15, wherein a number of inter office calls isdetermined from a numbering plan area code plus an exchange number.